Machine tool and control apparatus of the machine tool

1. A machine tool comprising:

a workpiece holding unit to hold a workpiece;

a tool rest to hold a cutting tool for cutting the workpiece;

a feeding unit to feed the cutting tool toward the workpiece in a predetermined feeding direction via relative movement between the workpiece holding unit and the tool rest;

a repetitive movement unit to reciprocally vibrate the workpiece holding unit and the tool rest in a mutually relative manner by repeating the relative movement in the feeding direction; and

a rotating unit to relatively rotate the workpiece and the cutting tool;

wherein the machine tool is capable of machining the workpiece via the relative rotation between the workpiece and the cutting tool and via the feeding of the cutting tool toward the workpiece with the reciprocal vibration; and

wherein the repetitive movement unit is configured so that the cutting tool performs one vibration with respect to multiple relative rotations between the workpiece and the cutting tool and so that a rotation angle of the relative rotation during a backward movement is smaller than a rotation angle of the relative rotation during a forward movement in one reciprocal vibration.

2. The machine tool according to claim 1 , wherein:

a reference angle position is set on the basis of a rotation angle position of the relative rotation at which a cutting work position of the forward movement and a cutting work position of the backward movement intersect with each other; and

the repetitive movement unit is configured so that, during one rotation from the reference angle position after the forward movement is performed for the length of a predetermined number of the relative rotations from the reference angle position, the forward movement switches to the backward movement and the cutting work position of the backward reaches the cutting work position of the forward movement to complete one reciprocal vibration.

3. The machine tool according to claim 1 , including a control apparatus for controlling said feeding unit, said repetitive movement unit and said rotating unit.

4. A machine tool comprising:

a cutting tool for cutting a workpiece;

a rotating unit to relatively rotate the cutting tool and the workpiece;

a feeding unit to feed the cutting tool and the workpiece in a predetermined feeding direction; and

a repetitive movement unit to reciprocally vibrate the cutting tool and the workpiece in a mutually relative manner in the feeding direction;

wherein the machine tool is capable of machining the workpiece via the relative rotation between the cutting tool and the workpiece and via the feeding of the cutting tool toward the workpiece with the reciprocal vibration and the repetitive movement unit is configured to vibrate so that a cutting work position of a forward movement of the reciprocal vibration overlaps with a cutting work position of a backward movement of the reciprocal vibration;

wherein the repetitive movement unit is configured to vibrate the cutting tool and the workpiece so that a rotation angle of the relative rotation during the backward movement is smaller than a rotation angle of the relative rotation during the forward movement during one vibration while the cutting tool performs one vibration with respect to multiple relative rotations between the cutting tool and the workpiece;

wherein a reference angle position at which the one vibration is complete is set by adding a predetermined rotation angle including a zero degree to a rotation angle position of the relative rotation at which the cutting work position of the forward movement comes into contact with the cutting work position of the backward movement; and

the repetitive movement unit is configured so that, during one rotation of up to the reference angle position after the forward movement is performed for the length of a predetermined number of the relative rotations, the forward movement switches to the backward movement and the cutting work position of the backward movement overlaps with the cutting work position of the forward movement.

5. The machine tool according to claim 4 , including a control apparatus for controlling said rotating unit, said feeding unit, and said repetitive movement unit.